Radiant energy is used in a variety of manufacturing processes to treat surfaces, films, and coatings applied to a wide range of materials. Specific processes include, but are not limited to, curing (i.e., fixing, polymerization), oxidation, purification, and disinfection. Processes employing radiant energy to polymerize or effect a desired chemical change are rapid and often less expensive compared to a thermal treatment. The radiation can also be localized to control surface processes and allow preferential curing only where the radiation is applied. Curing can also be localized within the coating or thin film to interfacial regions or in the bulk of the coating or thin film. Control of the curing process is achieved through selection of the radiation source type, physical properties (for example, spectral characteristics), spatial and temporal variation of the radiation, and curing chemistry (for example, coating composition).
A variety of radiation sources are used for curing, fixing, polymerization, oxidation, purification, or disinfections applications. Examples of such sources include, but are not limited to, photon, electron, or ion beam sources. Typical photon sources include, but are not limited to, arc lamps, incandescent lamps, electrodeless lamps and a variety of electronic and solid-state sources (i.e., lasers). Conventional arc type UV lamp systems and microwave-driven UV lamp systems use tubular bulb envelopes made of fused quartz glass or fused silica.
FIG. 1 is a perspective view of a microwave-powered UV curing lamp assembly showing an irradiator and a light shield assembly in the prior art. FIG. 2 is a partial cross-sectional view of the lamp assembly of FIG. 1 showing a half-elliptical primary reflector and a light source of circular cross-section. FIG. 3 is a partial cross-sectional internal view of the light shield assembly of FIG. 1 showing a half-elliptical primary reflector and a light source of circular cross-section mated to a secondary reflector and end reflectors.
Referring now to FIGS. 1-3, the apparatus 10 includes an irradiator 12 and a light shield assembly 14. The irradiator 12 includes a primary reflector 16 having a generally smooth half-elliptical shape with openings 18 for receiving microwave radiation to excite a light source 20 (to be discussed herein below), and a plurality of openings 22 for receiving air flow to cool the light source 20. The light source 20 includes a lamp (e.g., a modular lamp, such as a microwave-powered lamp having a microwave-powered bulb (e.g., tubular bulb with a generally circular cross-section) with no electrodes or glass-to-metal seals). The light source 20 is placed at the internal focus of the half-ellipse formed by the primary reflector 16. The light source 20 and the primary reflector 16 extend linearly along an axis in a direction moving out of the page (not shown). A pair of end reflectors 24 (one shown) terminate opposing sides of the primary reflector 16 to form a substantially half-elliptical reflective cylinder. The light shield assembly 14 of FIGS. 1-3 includes a secondary reflector 25 having a substantially smooth elliptical shape. A second pair of end reflectors 26 (one shown) terminates opposing sides of the secondary reflector 25 to form a substantially half-elliptical reflective cylinder.
A work piece tube 30 of circular cross-section is received in circular openings 28 in the end reflectors 26. The center of the openings 28 and the axis of the work piece tube 30 are typically located at the external focus of the half-ellipse formed by the primary reflector 16 (i.e., the foci of the half-ellipse formed by the secondary reflector 25). The work piece tube 28 and the secondary reflector 25 extend linearly along an axis in a direction moving out of the page (not shown).
In operation, gas in the light source 20 is excited to a plasma state by a source of radio frequency (RF) radiation, such as a magnetron 29 located in the irradiator 12. The atoms of the excited gas in the light source 20 return to a lower energy state, thereby emitting ultraviolet light (UV). Ultraviolet light rays 38 radiate from the light source 20 in all directions, striking the inner surfaces of the primary reflector 16, the secondary reflector 25, and the end reflectors 24, 26. Most of the ultraviolet light rays 38 are reflected toward the central axis of the work piece tube 30. The light source 20 and reflector design are optimized to produce the maximum peak light intensity (lamp irradiance) at a surface of a work product (also propagating linearly out of the page) placed inside the work piece tube 30.
FIG. 4 shows a plurality of cable connections between the irradiator 12 of FIGS. 1-3 and a conventional external power supply 40. Current irradiators manufactured by Fusion UV Systems of Gaithersburg, Md. are powered with high voltage DC and monitored for analog parameters, such as the detection and measurement of radio-frequency (RF) and ultraviolet (UV) radiation leakage. The external power supply 40 includes a three-phase power cable 42 for receiving conventional AC power. The external power supply 40 converts AC power to high voltage DC power in the range of 4 kV-7 kV DC. The high voltage DC power is applied to a high voltage HV cable 44 that extends between the external power supply 40 and the irradiator 12. The HV cable 44 typically includes seven analog signal wires (not shown): two wires for carrying the High Voltage (HV) DC power to the irradiator 12; two wires for powering a filament associated with a microwave-powered UV-emitting bulb 20 (i.e., the light source 20); one wire each for a photo detector and a pressure switch sensor; and a seventh wire for a cable interlock. An RF cable 46 for monitoring microwave leakage conditions is located between the external power supply 40 and an RF detector 48, which needs to be mounted close to the irradiator 12.
Unfortunately, the currently employed cables 44, 46 between the external power supply 40 and the irradiator 12 have a number of drawbacks. The cables 44, 46 have a limited range due to losses in the cable. Current irradiators 12 are not user friendly for product upgrading, standardizing and compatibility. For example, certain critical monitorable parameter, including UV power, temperature, air pressure, and part type require the installation of additional sensors inside the irradiator 12. The cables 44, 46 do not permit changes necessary to accommodate remote monitoring of the above-cited parameter because of limited I/O and significant tethering that requires close proximity of the external power supply 40 to the irradiator 12.
Current irradiators 12 do not permit the monitoring of UV output power that emanates from the UV-emitting bulb 20. Each UV-emitting bulb 20 is not identical in its UV output power. There are certain UV curing applications where multiple UV-emitting bulbs 20 are mounted adjacent to one another. Manual adjustments are required to lower or increase the voltage to equalize variations in UV output power from lamp to lamp. Therefore, it would be desirable to permit automatic monitoring and adjustment of UV output power.
Currently employed pressure switches (not shown) do not permit real time monitoring of air pressure inside the irradiator 12. The rate of flow of air inside the irradiator 12 is critical to the life of the UV-emitting bulb 20 and the magnetron 29. It is therefore desirable to install a monitorable pressure sensor that can transmit real time data back to a controller. Further, a monitorable pressure sensor can be integrated with a “smart blower” to automatically manage airflow and changing of speed of the “smart blower” based on data received from the monitorable pressure sensor.
Accordingly, what would be desirable, but has not yet been provided, is a microprocessor-controlled UV curing irradiator for monitoring internal sensors for performance parameters, part lifetime, and inventory control without necessitating major changes to a high voltage power supply.